(a) Field of the invention
The present invention uses a pneumatic device to drive a reciprocal driving device installed at one side of a main body and in turn driving a driving rod to enable reciprocal movement to a pumping device installed in an oil chamber at another side of the main body, with a sucking tube attached to a lower part of the main body reaching into an oil tank, thereby sucking oil into and out of the oil chamber.
(b) Description of the Prior Art
As shown in FIG. 9, the conventional manual type of oil pump includes an oil sucking tube 81 attached to a lower part of a main unit 8, a one-way valve installed inside the oil sucking tube 81, an oil discharge tube 82 attached to an upper part of the main unit 8, and a handle 83 attached to one side of the main unit 8. The inside of the main unit 8 is separated into two compartments, one containing a labor-saving gear set, another containing two sets of pump gears 84 in mesh (also shown in FIG. 10). When the handle 83 is turned, the labor-saving gear set is driven to rotate, which in turn drives the two pump gears 84 to rotate, creating a negative pressure inside the space below the two pump gears 84 and the sucking tube 81. The sucking tube 81 reaches inside the oil tank and can suck up the oil to pass between the two pump gears 84 before it is squeezed and discharged from the discharge tube 82.
Such oil sucking mechanism has the following shortcomings:    1. Manually turning the driving pump gear 84 costs time and labor, and cannot satisfy the requirements of high efficiency in liquid sucking speed and volume.    2. Generally excellent and close sliding contact must be maintained between the two sides and tooth surfaces of the pump gear 84 with the inside wall of the main unit 8. Extended wear and tear between the pump gear 84 and the main unit 8 will create a large clearance, resulting in backflow of oil and unsatisfactory oil sucking efficiency.